Karst is a repository for old sediments
Conference
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· Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:6949798
- Minnesota Geological Survey, St. Paul, MN (United States)
The Paleozoic plateau of southeastern Minnesota has been repeatedly glaciated, and has accumulated several sheets of loess. In the eastern part of this area, most of the older sediments have been eroded away and the late Wisconsinan Peoria loess directly overlies limestone. A lag of erratics from one or more older tills occurs sporadically on the bedrock surface. A more complete record is preserved in some sinkholes and solution cavities. Sinkholes (surface depressions) contain material that washed or collapsed into the hole, as well as material that was deposited directly (such as loess). Solution cavities contain only material sorted by water. Sinkhole fills exposed in roadcuts and quarry walls commonly lack the surface expression and black-dirt funnel'' of active sinkholes. Several of these contain erratic-bearing sediment interpreted as slopewash and mudflow. One appears to contain actual till--unsorted, unbedded pebble-loam that is not mixed with other materials commonly found on the limestone surface, such as red clay or loess. It cannot be determined whether this material was deposited directly or collapsed in later. Solution cavities are typically packed with sediment right up to the top. The bulk of such deposits is typically clay and silt; however, erratic pebbles are present in some. The fine sediment is sorted and bedded, at least in places. In one large cavity fill, a layer of rip-up clay clasts occurs near the top. Study of the stratigraphy of karst sediments in southeastern Minnesota is still preliminary. Techniques which are used to correlate them include: physical characteristics, texture analysis (on material that has not been sorted), sand and pebble lithology, and magnetic polarity. Techniques that could be used include clay mineralogy, geochemical analysis, and thermoluminescence.
- OSTI ID:
- 6949798
- Report Number(s):
- CONF-9404217--
- Conference Information:
- Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 26:5
- Country of Publication:
- United States
- Language:
- English
Similar Records
Magnetic susceptibility and feldspar zonations in the Peoria Loess and Roxana Silt of southwestern Illinois and eastern Missouri: Correlation tools and provenance indicators
Paleopedology of the Sangamonian-Wisconsinan transition in loess of the upper Mississippi Valley Driftless Area, Wisconsin
Late Quaternary land-sea correlations, northern Labrador, Canada
Conference
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Sun Feb 28 23:00:00 EST 1993
· Geological Society of America, Abstracts with Programs; (United States)
·
OSTI ID:5025436
Paleopedology of the Sangamonian-Wisconsinan transition in loess of the upper Mississippi Valley Driftless Area, Wisconsin
Conference
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Tue Dec 31 23:00:00 EST 1991
· Geological Society of America, Abstracts with Programs; (United States)
·
OSTI ID:5807834
Late Quaternary land-sea correlations, northern Labrador, Canada
Conference
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Mon Dec 31 23:00:00 EST 1984
· Geol. Soc. Am., Abstr. Programs; (United States)
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OSTI ID:6646681